1. Field of the Invention
The present invention relates to a process for producing a .beta.-silicon carbide fine powder.
2. Description of the Prior Art
Silicon carbide, which is very hard and has excellent properties such as resistance to oxidation, resistance to corrosion, resistance to spalling, hot strength, etc., finds a wide range of applications including in heat refractory industrial materials, but especially in applications such as lapping materials, pigments, matrix materials for heat refractory products, sintered silicon carbide, etc. There is a demand for a fine powder and a highly active silicon carbide. .beta.-Silicon carbide is called "low temperature" type silicon carbide based on its transition temperature and it is useful because it is a fine powder and is highly active as compared with .alpha.-silicon carbide, but various difficulties accompany its production.
That is, although some processes for producing .beta.-silicon carbide fine powder have been disclosed in, for example, British Pat. No. 1,199,953, Japanese Patent Application (OPI) Nos. 75600/75 and 37898/76, such prior art processes require, in addition to the complicated preparation of raw materials, an oxygen-free atmosphere when heating, high temperatures exceeding 1,450.degree. C. and an extended heating time to produce .beta.-silicon carbide in high quality and high yield. Accordingly, the prior art manufacture is highly restricted. It requires inefficient, unproductive and uneconomical special equipment such as a high temperature variable atmosphere oven, thus making .beta.-silicon carbide fine powder far less available and its commercial applications therefore limited.
As a process to greatly relax the restrictions on the above prior art processes, the applicants have recently been presented U.S. Pat. No. 4,117,096 directed to a new process for the mass production of high purity .beta.-silicon carbide by heating metallic silicon powder and carbon powder in an oxidizing atmosphere to induce a spontaneous chain reaction. Even with this process, however, and especially when a minute particle size on the order of submicrons is desired, it is necessary to reduce the packing density of the mixture of raw materials charged to a refractory reactor or to thoroughly pulverize the reaction product. The reduction in packing density inevitably leads to less productivity whereas the pulverization of the reaction product not only wastes more energy as the desired particle size becomes smaller but also increases abrasion of the pulverizer at the same time causing deterioration of the powder quality of the product.